1. Field of the Invention
The present invention relates to a structure having pores and its manufacturing method. The structure having pores obtained through this invention has a wide area of application such as functional materials and structural materials for electronic devices, memory media and memory devices. More particularly, the structure with pores can be used in vertical magnetic recording media, solid-state magnetic memory, magnetic sensor and photonic device.
2. Related Background Art
While the present invention concerns structures with pores, it is applicable without depending on the hole diameter of the pores.
A technical background centering on nano-size structures will be explained here because of the heightened interest in recent years on nano-size (structures ranging in size from about 0.1 nm to 200 nm) structures having pores (hereafter, referred to as “nano structure”).
Moreover, while there is no doubt that the reason nano structures have garnered interest is because of the anticipation of various effects due to their small sizes (for example in increasing the density of recording media), it is also because metals, thin-film semiconductors, fine wires and dots display unique electrical, optical and chemical properties as electron movements are sealed in sizes that are smaller than certain characteristic lengths.
Some of the manufacturing methods for nano structures include fine pattern drawing technology, such as photolithography, electron beam exposure and X-ray exposure that use semiconductor processing technology. Problems that have been pointed out in nano structure manufacturing methods using semiconductor processing technology include poor yield and the high cost of equipment. Thus, simple manufacturing methods with excellent reproductive qualities have been sought.
As a simple manufacturing method mentioned above, there is an attempt to realize a new nano structure based on a structure formed through self-organization, that is a systematic structure formed naturally. Many research projects are now under way for this technology because of the possibility of creating structures that are finer and more unique than those created through traditional methods, depending on the fine structure used as the base.
An example of a unique structure formed through self-organization is anodically oxidized alumina film (for example, see R. C. Furneaux, W. R. Rigby & A. P. Davidson “Nature” Vol. 337, P147 (1989)). The following is an explanation on the aforementioned positive pole oxide alumina film, using specific drawings.
FIGS. 1 and 2 schematically show cross-sectional views when anodically oxidized alumina nano holes are created on aluminum plates (or films). When an aluminum plate is anodically oxidized with acid electrolyte solution, a multi-pored oxidized film is formed. In FIG. 1 (A), reference numeral 114 denotes a nano hole, reference numeral 115 denotes an anodically oxidized film, and reference numeral 122 denotes a barrier layer. Also, a barrier layer means an insulated region comprising alumina that exists at the bottom surface of the pore section of anodically oxidized film 115.
FIG. 1 (B) schematically shows a cross section of an aluminum (Al) film on the substrate that has been anodically oxidized mid way. In this figure, reference numeral 123 denotes a substrate, and reference numeral 124 denotes an aluminum film.
The characteristics of this multi-pored oxidized film are the fact that the fine and cylindrical nano holes (pores) 114 with extremely small diameters (2r) of several nm to several hundred nm, features a unique geometrical structure of aligning parallel at an interval of several tens nm to several hundred nm, as shown in FIG. 1 (A).
Also, various applications are being attempted to utilize the uniquely geometrically structured anodically oxidized alumina nano holes.
For example, some applications concern the use of anodically oxidized films for their wear-resistance property or insulation-resistance properties. There is also an application of anodically oxidized films substance as filter after separating the films. Further, there are various attempts to develop technology to fill the nano hole with metal, semiconductor or magnetic material, or using the replica technology for coloring, magnetic recording media, EL light emitting devices, electro-chromic devices, optical devices, solar cells and gas sensors. There are many other anticipated application areas such as quantum fine wires, MIM devises and other quantum effect devices, and molecular sensors that use nano holes as the venue for chemical reaction. Moreover, a detailed description of nano hole is shown in Masuda “Solid State Logic” 31,493 (1996).
However, there were various limitations in the development of devices using the above-mentioned nano hole layers because, as shown in FIGS. 1 (A) and 1 (B), the conventional support material that comes in contact with anodically oxidized alumina hole layer is limited to aluminum plate 121 (or aluminum film 124).